From 7dc924e90997da093d8293dd5f82eb8c2fc2ef29 Mon Sep 17 00:00:00 2001
From: tkaunlaky-e6 <tanay@e6x.io>
Date: Fri, 6 Mar 2026 13:54:20 +0530
Subject: [PATCH] Add NEXT_DAY transpilation from Databricks to E6

Transpile NEXT_DAY(expr, dayOfWeek) to:
CAST(DATE_ADD(expr, MOD((target_index - DAYOFWEEK(expr) + 6), 7) + 1) AS DATE)
---
 sqlglot/dialects/databricks.py |  1 +
 sqlglot/dialects/e6.py         | 67 ++++++++++++++++++++++++++++++++++
 sqlglot/expressions.py         |  5 +++
 3 files changed, 73 insertions(+)

diff --git a/sqlglot/dialects/databricks.py b/sqlglot/dialects/databricks.py
index 325c4ec6f1..10a5a1d602 100644
--- a/sqlglot/dialects/databricks.py
+++ b/sqlglot/dialects/databricks.py
@@ -140,6 +140,7 @@ class Parser(Spark.Parser):
             "DATEDIFF": build_date_delta(exp.DateDiff),
             "DATE_DIFF": build_date_delta(exp.DateDiff),
             "FIND_IN_SET": exp.FindInSet.from_arg_list,
+            "NEXT_DAY": exp.NextDay.from_arg_list,
             "GETDATE": exp.CurrentTimestamp.from_arg_list,
             "GET_JSON_OBJECT": _build_json_extract,
             "TO_DATE": build_formatted_time(exp.TsOrDsToDate, "databricks"),
diff --git a/sqlglot/dialects/e6.py b/sqlglot/dialects/e6.py
index 3e1ab6b2a8..c13ca0eee2 100644
--- a/sqlglot/dialects/e6.py
+++ b/sqlglot/dialects/e6.py
@@ -1940,6 +1940,72 @@ def _last_day_sql(self: E6.Generator, expression: exp.LastDay) -> str:
                 return self.func("LAST_DAY", date_expr, unit)
             return self.func("LAST_DAY", date_expr)
 
+        # Mapping from day-of-week abbreviations/names to DAYOFWEEK index (1=Sunday .. 7=Saturday)
+        _DAY_OF_WEEK_INDEX: t.ClassVar[t.Dict[str, int]] = {
+            "SU": 1,
+            "SUN": 1,
+            "SUNDAY": 1,
+            "MO": 2,
+            "MON": 2,
+            "MONDAY": 2,
+            "TU": 3,
+            "TUE": 3,
+            "TUESDAY": 3,
+            "WE": 4,
+            "WED": 4,
+            "WEDNESDAY": 4,
+            "TH": 5,
+            "THU": 5,
+            "THURSDAY": 5,
+            "FR": 6,
+            "FRI": 6,
+            "FRIDAY": 6,
+            "SA": 7,
+            "SAT": 7,
+            "SATURDAY": 7,
+        }
+
+        def _next_day_sql(self: E6.Generator, expression: exp.NextDay) -> str:
+            date_expr = expression.this
+            day_expr = expression.expression
+
+            # If the day-of-week argument is a string literal, resolve it to an integer index
+            if isinstance(day_expr, exp.Literal) and day_expr.is_string:
+                day_name = day_expr.this.upper()
+                target_index = self._DAY_OF_WEEK_INDEX.get(day_name)
+                if target_index is not None:
+                    # CAST(DATE_ADD(expr, (target_day_index - DAYOFWEEK(expr) + 6) % 7 + 1) AS DATE)
+                    # The +6 (instead of +7) combined with +1 ensures that if expr
+                    # is already the target day, we skip to the next week (7 days).
+                    date_add = exp.Anonymous(
+                        this="DATE_ADD",
+                        expressions=[
+                            date_expr,
+                            exp.Add(
+                                this=exp.Mod(
+                                    this=exp.Paren(
+                                        this=exp.Add(
+                                            this=exp.Sub(
+                                                this=exp.Literal.number(target_index),
+                                                expression=exp.Anonymous(
+                                                    this="DAYOFWEEK", expressions=[date_expr.copy()]
+                                                ),
+                                            ),
+                                            expression=exp.Literal.number(6),
+                                        )
+                                    ),
+                                    expression=exp.Literal.number(7),
+                                ),
+                                expression=exp.Literal.number(1),
+                            ),
+                        ],
+                    )
+                    return self.sql(
+                        exp.Cast(this=date_add, to=exp.DataType(this=exp.DataType.Type.DATE))
+                    )
+
+            raise ValueError(f"NEXT_DAY: unsupported day-of-week: {self.sql(day_expr)}")
+
         def extract_sql(self: E6.Generator, expression: exp.Extract | exp.DayOfYear) -> str:
             unit = expression.this.name
             unit_mapped = E6.UNIT_PART_MAPPING.get(f"'{unit.lower()}'", unit)
@@ -2848,6 +2914,7 @@ def create_lpad_component(func_name: str):
             exp.JSONObject: lambda self, e: self.func("NAMED_STRUCT", e.this, *e.expressions),
             exp.LastDay: _last_day_sql,
             exp.LastValue: rename_func("LAST_VALUE"),
+            exp.NextDay: _next_day_sql,
             exp.Length: length_sql,
             exp.Log: lambda self, e: self.func("LOG", e.this, e.expression),
             exp.Lower: rename_func("LOWER"),
diff --git a/sqlglot/expressions.py b/sqlglot/expressions.py
index f7d2a9b11f..e21b466d0c 100644
--- a/sqlglot/expressions.py
+++ b/sqlglot/expressions.py
@@ -6055,6 +6055,11 @@ class LastDay(Func, TimeUnit):
     arg_types = {"this": True, "unit": False}
 
 
+class NextDay(Func):
+    _sql_names = ["NEXT_DAY"]
+    arg_types = {"this": True, "expression": True}
+
+
 class Extract(Func):
     arg_types = {"this": True, "expression": True}